1. Field of the Invention
Embodiments of the invention relate to an organic light emitting diode display device and a method of manufacturing the same, and more particularly, to an organic light emitting diode display device and a method of manufacturing the same achieving high resolution in large size.
2. Discussion of the Related Art
Recently, many efforts and studies have been being made to develop flat panel displays, such as liquid crystal display (LCD) devices and organic light emitting diode (OLED) display devices, as substitute for cathode-ray tubes (CRTs).
Of these flat panel displays, since the OLED display devices are self-luminescent without a need for a light source, have a thinner profile, are lighter weight, and have better color reproduction than the LCD devices, the OLED display devices have come into the spotlight as next-generation display devices.
The OLED display device is generally categorized into a passive type and an active type. Among these types, the active type OLED display device, which includes a thin film transistor in each pixel and has low power consumption and advantage in resolution, is widely used to realize a high-resolution and large-sized image display device.
FIG. 1 is a cross-sectional view illustrating an active type OLED display device according to a related art. Referring to FIG. 1, in the related art OLED display device, a semiconductor layer 101 and a first storage electrode 102 are formed on a substrate 100. On the semiconductor layer 101 and the second storage electrode 102, a gate electrode 111, a source electrode 121, a drain electrode 122, a second storage electrode 112 and a third storage electrode 123 are formed with a plurality of insulating layers 110, 120, 130 and 140 located thereamong.
A gate pad 124 connected with a gate electrode of a switching transistor and a data pad 125 connected with a source electrode of the switching transistor are formed below the third insulating layer 130.
The source electrode 121 and the drain electrode 122 are formed on the second insulating layer 120, and the drain electrode 122 is connected with an anode 141. An organic light emitting layer 151 is formed on the anode 141 and a bank layer 150 formed on the fourth insulating layer 140.
A second storage electrode 112 is formed on the first insulating layer 110 corresponding to the first storage electrode 102. In a similar manner, a third storage electrode 123 is formed on the second insulating layer 120 corresponding to the second storage electrode 112. The storage electrodes 102, 112 and 123 function to produce a capacitance and maintain light emission of the organic light emitting layer 151 even when a gate signal is not applied. As the number of the storage electrodes 102, 112 and 123 is increased a capacitance sufficient to operate the organic light emitting layer 151 is achieved. However, since a size of each pixel region is limited, circuit design reducing the occupied area of the storage electrodes is required in order to achieve high resolution with high integration in the space limited pixel region.
Regarding a large-sized panel, a voltage drop occurs as a pixel is farther from a power supply terminal. If the voltage drop is not compensated, disuniformity of brightness may occur. Since the pixel regions have the same limited area, as components for compensation circuits including the storage electrodes increase, degree of integration is reduced and high resolution is thus difficult to achieve.
Further, since a third contact hole 140a is formed by etching two layers, and in particular, a height of the fourth insulating layer 140 formed for planarization is great, a step of the third contact hole 140a formed in the fourth insulating layer 140 is greater than other contact holes. The anode 141 formed on the third contact hole 140 having the great step is uneven in thickness or partially cut, and this may cause problems in electric connection.
Further, the gate pad 124 and the data pad 125 are exposed after the fourth contact hole 140b and the fifth contact hole 140c are formed. When the pads 124 and 125 are exposed for a long time until a layer is formed thereon, the pads 124 and 125 may be oxidized and damaged. The damage of the pads 124 and 125 may cause an unstable electric connection.
Among the storage electrodes 102, 112 and 123, the second storage electrode 112 and the third storage electrode 123 are made of metal while the first storage electrode 102 is made of a silicon group material, which is the same one of the semiconductor layer 101. Accordingly, to use the first storage electrode 102 as an electrode, an additional semiconductor process such as a doping process is required, and this reduces process efficiency.